Compressibility measurements of quasi-one-dimensional quantum wires

TL;DR

This study measures the compressibility of a 1D quantum wire in a GaAs/AlGaAs heterostructure, revealing insights into spin-related phenomena and challenging some existing models of the 0.7 conductance anomaly.

Contribution

It introduces a sensitive technique to measure wire compressibility and provides experimental evidence supporting spontaneous spin polarization as the origin of the 0.7 structure.

Findings

Detects spin-splitting of subbands with magnetic field

Observes the 0.7 structure's behavior with temperature and field

Finds no evidence for the Kondo quasibound state

Abstract

We report measurements of the compressibility of a one-dimensional (1D) quantum wire, defined in the upper well of a GaAs/AlGaAs double quantum well heterostructure. A wire defined simultaneously in the lower well probes the ability of the upper wire to screen the electric field from a biased surface gate. The technique is sensitive enough to resolve spin-splitting of the subbands in the presence of an in-plane magnetic field. We measure a compressibility signal due to the 0.7 structure and study its evolution with increasing temperature and magnetic field. We see no evidence of the formation of the quasibound state predicted by the Kondo model, instead our data are consistent with theories which predict that the 0.7 structure arises as a result of spontaneous spin polarization.